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WASHINGTON — The Pentagon is reviewing its war database to prepare for potential fallout from WikiLeak's expected release of secret documents related to the Iraq war, according to NBC News.

The release could come as early as Sunday evening.

"The problem is we have no idea what WikiLeaks has or is going to release, so we're preparing for the worst," one senior Pentagon official told NBC News on Friday.

WikiLeaks, the controversial online organization set up to reveal government secrets, has indicated it would release as many as 400,000 classified logs from Iraq. In July, WikiLeaks released at least 75,000 classified U.S. military documents on the Afghan war, including the names of informants and other strategic reports in Afghanistan.

U.S. officials have warned that public revelations about intelligence information can have unpredictable consequences, potentially undermining efforts to monitor and disrupt militants plotting attacks.

Pentagon officials told NBC News they were scouring over 400,000 documents from Iraq they suspect could be what WikiLeaks plans to release next.

Pentagon and military officials say there have been no conversations between WikiLeaks and the Pentagon about redacting highly sensitive or life-threatening information from any classified documents that may be released.

Earlier this year, Pfc. Bradley Manning, an Army intelligence analyst, was charged with providing a classified video to the whistle-blower website.

Manning, 22, is charged with leaking video of a 2007 U.S. Apache helicopter attack in Baghdad that killed a Reuters news photographer and his driver. WikiLeaks posted the video on its website in April.

Military investigators say Manning also is a person of interest in the July leak of the Afghanistan documents.

The Pentagon has concluded that no U.S. intelligence sources or practices were compromised by the posting of secret Afghan war logs by WikiLeaks, but the military thinks the leaks could still cause significant damage to U.S. security interests.

The assessment, outlined in a letter obtained Friday by The Associated Press, suggests that some of the Obama administration's worst fears about the July disclosure have so far failed to materialize.

Defense Secretary Robert Gates reported these conclusions in an Aug. 16 letter to Sen. Carl Levin, chairman of the Senate Armed Services Committee, who had requested a Pentagon assessment.

U.S. officials warned of dire consequences in the days following the July leak. In his letter to Levin, Gates struck a more measured tone in describing the impact.

"Our initial review indicates most of the information contained in these documents relates to tactical military operations," Gates wrote, suggesting the materials did not include the most sensitive kinds of information.

"The initial assessment in no way discounts the risk to national security; however, the review to date has not revealed any sensitive intelligence sources and methods compromised by this disclosure," he added.

A Pentagon spokesman, Marine Col. David Lapan, said Friday that the assessment of the July documents is still valid, even after a more thorough review. A special task force led by the Defense Intelligence Agency combed the posted reports for weeks to determine what might have been compromised.

Names of intelligence sources generally are classified at a higher level than the secret-level documents published by WikiLeaks. The documents provided a ground-level view of the war, from 2004 through 2009, based largely on narrow intelligence reports and other battlefield materials.

Gates noted that the documents contained the names of "cooperative Afghan nationals." These were not secret intelligence sources but Afghans who had decided to cut their ties to the Taliban.

The Taliban later vowed to punish these individuals, if the reports proved true.

"We assess this risk as likely to cause significant harm or damage to the national security interests of the United States and are examining mitigation options," Gates wrote. "We are working closely with our allies to determine what risks our mission partners may face as a result of the disclosure."

So far, the Pentagon has not reported any incidents of reprisals against Afghans named in the leaked documents.

More recently, U.S. intelligence officials have said the July disclosures sharpened a debate over how far to go in sharing sensitive information within the government, a practice that expanded after Sept. 11, 2001, in order to help prevent future terrorist attacks.

In a speech Oct. 6 to the Bipartisan Policy Center, the director of national intelligence, James Clapper, called the July leaks "a big yellow flag" for those concerned about protecting classified information.

"I think it's going to have a very chilling effect on the need to share," Clapper said.